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A transition metal diphosphide, WP2, is a candidate for type‐II Weyl semimetals (WSMs) in which spatial inversion symmetry is broken and Lorentz invariance is violated. As one of the prerequisites for the presence of the WSM state in WP2, spatial inversion symmetry breaking in this compound has rarely been investigated. Furthermore, the anisotropy of the WP2 electrical properties and whether its electrical anisotropy can be tuned remain elusive. Angle‐resolved polarized Raman spectroscopy, electrical transport, optical spectroscopy, and first‐principle studies of WP2 are reported. The energies of the observed Raman‐active phonons and the angle dependences of the detected phonon intensities are consistent with results obtained by first‐principle calculations and analysis of the proposed crystal symmetry without spatial inversion, showing that spatial inversion symmetry is broken in WP2. Moreover, the measured ratio (Rc /Ra ) between the crystalline c‐axis and a‐axis electrical resistivities exhibits a weak dependence on temperature (T) in the temperature range from 100 to 250 K, but increases abruptly at T ≤ 100 K, and then reaches the value of ≈8.0 at T = 10 K, which is by far the strongest in‐plane electrical resistivity anisotropy among the reported type‐II WSM candidates with comparable carrier concentrations. Optical spectroscopy study, together with the first‐principle calculations on the electronic band structure, reveals that the abrupt enhancement of the electrical resistivity anisotropy at T ≤ 100 K mainly arises from a sharp increase in the scattering rate anisotropy at low temperatures. More interestingly, the Rc /Ra of WP2 at T = 10 K can be tuned from 8.0 to 10.6 as the magnetic field increases from 0 to 9 T. The so‐far‐strongest and magnetic‐field‐tunable electrical resistivity anisotropy found in WP2 can serve as a degree of freedom for tuning the electrical properties of type‐II WSMs, which paves the way for the development of novel electronic applications based on type‐II WSMs.

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A peakZTvalue of 0.66 at 675 K is reached for Bi2S3added with 1.0 mol% ZnO.

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As a cheap substitute for PbTe or PbSe, the thermoelectric performance of PbS still remains to be improved. In this report, we selected BiS as a donor and employed a facile route of hydrothermal synthesis combined with microwave sintering to fabricate BiS doped PbS. Due to the increased electrical conductivity by BiS doping and the decreased thermal conductivity from the refined microstructure, the thermoelectric figure of merit ZT of microwave sintered PbBiS and PbBiS reached 0.90 and 0.86 at 800 K, respectively, without sign of saturation. When processed with plasma activated sintering (PAS), the highest ZT value of PbBiS only reached 0.3 at 800 K. The obtained results indicate that hydrothermal synthesis and microwave sintering can essentially improve the thermoelectric properties of PbBiS and easily realize mass production at low cost.

The systematic evolution of the structural, vibrational, and superconducting properties of nearly optimally doped Tl2Ba2CaCu2O(8+δ) with pressure up to 30 GPa is studied by x-ray diffraction, Raman scattering, and magnetic susceptibility measurements. No phase transformation is observed in the studied pressure regime. The obtained lattice parameters and unit-cell volume continuously decrease with pressure by following the expected equation of state. The axial ratio of c/a exhibits an anomaly starting from 9 GPa. At such a pressure level, the deviation from the nonlinear variation of the phonon frequencies is detected. Both the above observations indicate the enhancement of the distortion upon compression. The superconducting transition temperature is found to exhibit a parabolic behavior with a maximum of 114 K around 7 GPa. We demonstrate that the interplay between the intrinsic pressure variables and distortion controls the superconductivity.

In this paper, the influence of surface charges is quantitatively analyzed based on the study of surface charge distribution under DC voltage and flashover characteristics of insulators under superimposed voltage of DC and lightning impulse. It is found that when DC and impulse voltage are in the same polarity, surface charges weaken the electric field along the insulator surface and flashover voltages under superimposed voltage increases. When DC and impulse are in the opposite polarity, surface charges enhance the electric field along the insulator surface, and flashover voltages will decrease. The calculation results of the electric field along the flashover path show that the changing rate of the maximum field strength is approximately equal to the changing rate of flashover voltage, which proves that the influence of surface charges on flashover characteristics of insulators mainly depends on their distortion of the electric field.